Flexible corrugated-wall elliptical-cross-section waveguide useful for propagating only one polarization of fundamental mode



g- 1965 E. SCHUTTLOFFEL ETAL 3,200,356

FLEXIBLE CORRUGATED-WALL ELLIPTICALPCROSS-SECTION WAVEGUIDE USEFUL FOR PROPAGATING ONLY ONE POLARIZATION 0F FUNDAMENTAL MODE Filed July 2 1962 INVENIORS Erich Schiit'rlffel 8 Wolfgang Krcmk ATTORNEY United States Patent 3,206,356 FLEXIBLE CORRUGATED-WALL ELLIPHCAL- CRQtiS-SEQTIQN WAVEGUIDE USEFUL FUR PRGPAGAHNG ONLY ONE PULARHZATIUN @F FUNDAMENTAL MQDE Erich Schiittliilfel and Wolfgang Kranlr, Bachnaug, Wurttemherg, Germany, assignors to Telefunlren Patentverwertungs-G.rn.h.H., Ulrn (Danube), Germany Filed duly 2, 19-52, Ser. No. 296,814 laims priority, application Germany, June 3d, 196i,

T 20,366 Claims. (Cl. 333-95) The present invention relates to an arrangement for the transmission of linearly polarized plane electromagnetic waves of very high frequency with little damping, which is especially suited for the transmission of broad frequency bands.

It is known to use waveguides or coaxial cables or lines, for example, between a receiver and an antenna for transmitting microwaves. When it was required that these lines be flexible and capable of being wound onto a drum, coaxial lines were preferably used. Such coaxial lines, however, provide too much damping at correspondingly high frequencies. Besides, it is not possible to choose the diameter of the outer line or conductor at random, and thus it is likewise impossible to choose the diameter of the inner line or conductor at random at a certain characteristic impedance, as there is the possibility that an H wave will be excited.

Furthermore, flexible round waveguides are known for transmitting microwave energy. However, these have the disadvantage that when transmitting linearly polarized plane electromagnetic waves, the position of the polarization direction may change uncontrollably. if, for transmission purposes, flexible rectangular waveguides of known type are used, there is the disadvantage that these waveguides are hardly capable of being wound onto a drum.

Attempts have been made to use a flexible round waveguide for the transmission of microwaves which can be wound onto a drum. Here, the sleeve of a coaxial corrugated cable was used without the inner line and without the supports necessary for such inner line. In order to achieve suficient flexibility, the groove or corrugations of such corrugated cable must have a certain depth. However, due to this, undesired modes of oscillation are excited and/or the linearly polarized plane Wave which is fed to this cable is separated into two C04 1 ponents. As mentioned above, a change in the polarization direction results, which is dependent upon the length and the curvature. Besides, the separation into two components, as well as the change in the polarization direction is highly dependent upon the frequency. If a broad requency band has to be transmitted via such a line, decoupling or detuning of the energy fed to it is not possible without incurring great losses.

With these defects of the prior art in mind, it is a main object of the present invention to provide a new arrangement which avoids the disadvantages of tre previ ously known arrangements, without impairing the electrical properties.

Another object of the instant invention is to provide a device of the character described having low damping features.

A further object of the invention is to provide a microwave device wherein the direction of the polarization is definite and will not be changed.

Still a further object is to provide a device of the type described which is sufficiently flexible to be wound onto a drum or the like.

These objects and others ancillary thereto are accomplished according to preferred embodiments of the invention wherein the device is of the type for transmitting linearly polarized plane electromagnetic waves of very high frequency with little damping, and which is capable of being wound onto a drum, and is especially suitable for transmitting broad frequency bands. The device is a corrugated hollow line with suitable devices for coupling and decoupling, and this corrugated hollow line has an elliptical cross section, whereby the devices for coupling and decoupling are provided at the ends of the arrangement and are mounted at right angles to the major axis of the elliptical cross section of the corrugated hollow line. Also, additional means may be provided at the ends of this arrangement for suppressing undesirable modes of oscillation.

The above-mentioned means for suppressing undesired modes or oscillation are preferably arranged and con 5 structed in such a manner that they do not influence the coupling and decoupling devices, i.e., they are decoupled with respect to these devices.

Additional objects and advantages of the present in vention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic elevational view of an arrangement constructed in accordance with the present invention.

FIGURE 2 is a cross-sectional view along the line 22.

FIGURE 3 is a cross-sectional view along the line 3-3.

FIGURE 4 is a cross-sectional view along the line 4-4.

With more particular reference to the drawings, FIG- URE 1 shows a section of an elliptical corrugated hollow line 1 of any desired length. At the ends-of this line 1 coupling and decoupling devices are provided. in the embodiment illustrated, these coupling devices comprise two coupling lugs 2 and 6 located in hollow line sections 3 and '7 which may connect the transmitter and antenna, for example.

The hollow line sections 3 and '7 may have a round or a square cross section. Since the corrugated hollow line it has an elliptical cross section, intermediate sections 5 and 9 are also used in this embodiment to provide a transition from the elliptical cross section of the corrugated hollow line 1 to the waveguide sections 3 and 7 which are adjacent thereto on each end, respectively. The cross section of these waveguide sections 3 and "7 is round or square, according to the particular purpose for which the arrangement is used. The intermediate sections 5 and 9 may have a cross section which is flaring and has a uniform increase in cross section, or they may have a cross section which changes stepwise from one cross sectional area to another.

By shaping the corrugated hollow line to be elliptical in cross section, the separation and shifting of the transmitted wave, which occurs in the case of the known arrangements, is reduced to a minimum without the flexibility of the arrangement being impaired. The minimal undesired separation which is still present and which is created in the corrugated hollow line 1 and/or at the transitions from the elliptical to the round and/ or square cross sections of the adjoining waveguide sections, may under some circumstances lead to great damping surges at certain frequencies. In order to prevent this, means are provided at the ends of the arrangement to suppress these undesired modes of oscillation. In the simplest case, these means are in the form of absorbers 4 and 8. Each of these absorbers comprises a piece of sheet metal which is arranged parallel to the coupling lugs Z and 6, respectively. The pieces of sheet metal (of the absorbers 4 and 8) are provided with an absorbing material, such as carbon.

7 By suitably and judiciously choosing the position of elements 4 and 8, undesired influences on the coupling and decoupling devices are prevented. If an absorber of known construction is provided at the ends of waveguide sections 3 and 7, respectively, and if a thin piece of sheet metal is additionally mounted between and parallel to elements 2 and 6, respectively, then the desired decoupling is likewise achieved. In the place of coupling lugs (2, 6) correspondingly shaped waveguide sections may be used, known in their art.

In the embodiment of the invention illustrated in FIG- URE l, a particular component is used at the ends of the corrugated hollow line 1, and this component contains the required coupling elements. This means that intermediate sections 5 and 9 are necessary for equating the various cross sections of these components.

Furthermore, the necessary coupling elements may be provided directly within the corrugated hollow line 1 together with the means for suppressing the undesired modes of oscillation. Here, also, the above-mentioned coupling lugs are especially well suited for coupling and/or decoupling the wave to be transmitted. The coupling devices used in this arrangement must then be mounted in such a manner that only the wave transmitted via the elliptical cross section of the corrugated hollow line 1 is taken into consideration, i.e., when using coupling lugs, these have to be mounted at right angles to the major axis of the elliptical cross section of the line.

The arrangement according to the invention provides for transmission of the desired linearly polarized plane electromagnetic wave, with little damping, whereby the transmission line may have a very small curvature. A curvature diameter which is smaller than 1 meter may be achieved. The term curvature diameter means the diameter of the drum onto which the transmission line may be wound. With respect to the flexible coaxial lines used heretofore, the damping in the arrangement of the present invention, with an equal amount of flexibility, is smaller by approximately the factor 2, i.e., the damping has a value which is in the range of a normal, non-flexible waveguide if this waveguide is operated in a frequency range in which no other wave form can be radiated.

The construction of the corrugated hollow line with elliptical cross section proposed in accordance with this invention can easily be accomplished. For instance, this may be achieved simply by pressing or flattening a corrugated hollow line with a round cross section, or by correspondingly constructing a cable-making machine which produces corrugated hollow lines. Because of the advantages provided by the present invention-small damping, capability of being wound onto a drum, unidirectionality of the transmitted wavesuch Without disturbing the electrical characteristics, like a coaxial cable.

2 That is the outer conductor of a heliuecoaxial-cable.

an arrangement is especially advantageous for waveguides which have to be mounted in a bent, tortuous, or curved manner, for example, for antenna feeding lines. Even if two types of polarization are fed to one antenna, the device of the present invention is substantially less expensive than the former method in which two coaxial lines or a round waveguide or two rigid rectangular waveguides were used.

For this pur ose, only two corrugated hollow lines constructed according to the invention are necessary, the mounting of which is, in addition, substantially simpler.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. In a waveguide device for transmitting linearly polarized plane electromagnetic waves of very high fre quency with little damping, especially for the transmission of broad frequency bands, and which is capable of being wound onto a drum, the device including a corrugated hollow line with corresponding coupling and decoupling devices, the improvement wherein the corrugated hollow line has an elliptical cross section, the coupling and decoupling devices are provided at the ends of the waveguide device and are arranged at right angles to the major axis of the elliptical cross section of the corrugated hollow line, and means are provided at the ends of the waveguide device for suppressing undesired modes of oscillation.

2. A waveguide device, for use in transmitting linearly polarized plane electromagnetic waves of very high frequency with low loss, said device comprising, in combination:

(a) a corrugated hollow line having an elliptical cross section;

(b) coupling and decoupling means connected to the ends of said line and disposed at right angles with the major axis of the elliptical cross section of said line; and

(c) means connected to the ends of said line for suppressing undesired modes of oscillation.

3. A device as defined in claim 2 wherein said suppressing means are arranged and constructed so as not to influence the coupling and decoupling means.

4. A device as defined in claim 3 wherein said suppressing means are in the form of absorbers.

5. A device as defined in claim 2 wherein said coupling and decoupling means and the means for suppressing the undesired modes of oscillation are provided directly within the corrugated hollow line.

6. A device as defined in claim 2 wherein said coupling means and said means for suppressing the undesired modes of oscillation are provided at the front end and at the rear end of the waveguide device in a separate component including a waveguide section.

7. A device as defined in claim 6 wherein said waveguide section is round in cross section.

8. A device as defined in claim 6 wherein said waveguide section is square in cross section.

9. A device as defined in claim 6 wherein an intermediate section is provided between the corrugatcd hollow line and the component which is provided with the coupling means.

10. A device as defined in claim 9 wherein said intermediate section flares and has a uniformly increasing cross section.

11. A device as defined in claim 9 wherein said intermediate section has a cross section which increases in stepwise manner.

12. A device as defined in claim 2 wherein said coupling and decoupling means includes coupling lugs.

13. A device as defined in claim 2 wherein said coupling and decoupling means includes correspondingly shaped waveguide sections.

14. In combination a transmitter; an antenna; and a waveguide device as defined in claim 2 connected therebetween for providing an antenna feeding line.

15. In a waveguide device for transmitting linearly polarized plane electromagnetic Waves of very high frequency with low loss especially for the transmission of broad frequency bands, the improvement comprising a hollow line having an elliptical cross section and being corrugated so that it is capable of being Wound onto a drum, and coupling and decoupling means connected at the ends of said line and disposed at right angles with the major axis of the elliptical cross section of said line.

References Cited by the Examiner UNITED STATES PATENTS 2,632,804 3/53 Jouguet 333-98 2,844,724 7/58 Fraser 333-98 X 2,924,797 2/ 6t) Robertson 333-98 3,019,399 1/62 Lanciani 33398 X FOREIGN PATENTS 748,152 4/56 Great Britain.

66,119 12/47 Denmark. 1,249,057 11/60 France. 1,099,602 2/61 Germany.

OTHER REFERENCES Ragan: Microwave Transmission Circuits, N.Y., Mc- Graw-Hill, 1948 (pages 54-58 and page 282 relied on).

Freedman: Flexible Wave Guide Radio and TV News, vol. 49, No. 6, pp. 7-9, June 1953.

Technical Report No. AF-87, May 1961, The Johns Hopkins University Radiation Laboratory, title page, abstract page and pages 7 and 13 cited.

HERMAN KARL SAALBACH, Primary Examiner. 

15. IN A WAVEGUIDE DEVICE FOR TRANSMITTING LINEARLY POLARIZED PLANE ELECTROMAGNETIC WAVES OF VERY HIGH FREQUENCY WITH LOW LOSS ESPECIALLY FOR THE TRANSMISSION OF BROAD FREQUENCY BANDS, THE IMPROVEMENT COMPRISING A HOLLOW LINE HAVING AN ELLIPTICAL CROSS SECTION AND BEING CORRUGATED SO THAT IT IS CAPABLE OF BEING WOUND ONTO A DRUM, AND COUPLING AND DECOUPLING MEANS CONNECTED AT THE ENDS OF SAID LINE AND DISPOSED AT RIGHT ANGLES WITH THE MAJOR AXIS OF THE ELLIPTICAL CROSS SECTION OF SAID LINE. 